There seems to be rumour and counter-rumour on this subject and certainly our contacts at Dell over here in the UK have certainly not indicated that their range would be dropped. In fact sales of the Dell x51V and other devices appear to be quite strong in the education sector at least.
There's some information regarding Dell's denial that they were intending to drop their handhelds in this story from Brighthand.com:
http://www.brighthand.com/default.asp?newsID=12206